Antitumor effects of vitamin A against Shope carcinoma cells

The antitumor effects of retinol were tested on three cell lines which were derived from a single Shope carcinoma and differed in their degree of differentiation. Addition of retinol to cultures induced growth retardation and morphological changes of these sublines. On removal of retinol from the culture medium, reversion of the undifferentiated subline was observed, but the two differentiated sublines did not revert. The tumorigenic potential of the differentiated sublines was lost or greatly reduced when they were injected into nude mice after 7 days of culture with retinol, whereas the potential of the undifferentiated subline was only slightly reduced. These results suggest that retinol may be effective against differentiated squamous cell carcinomas, but not against undifferentiated tumors.